WO2022041660A1

WO2022041660A1 - Freeze-thaw damage in situ monitoring device and method for underwater concrete member

Info

Publication number: WO2022041660A1
Application number: PCT/CN2021/075306
Authority: WO
Inventors: 鲍玖文; 于子浩; 张鹏; 李树国; 赵铁军
Original assignee: 青岛理工大学
Priority date: 2020-08-28
Filing date: 2021-02-04
Publication date: 2022-03-03
Also published as: US11946923B2; US20220308038A1; CN111965338A

Abstract

A freeze-thaw damage in situ monitoring device and method for an underwater concrete member. A body structure of the device comprises an upper connecting rod (1), a concrete member (2), a transverse sealing box (3), a longitudinal sealing box (4), a movable guide rod (5), a probe launch box (6), a multi-channel data collector (7), a frequency modulation transmitter (8), a computer (9), an auxiliary wheel (10), a lower connecting rod (11) and a wireless temperature sensor (12). The method comprises the four steps of launching a probe (613), acquiring data, calculating the elastic modulus and evaluating the freeze-thaw damage. The device is simple in structure, convenient to operate and can be used repeatedly; homopolar high-strength magnets are used to provide power for the launch of the probe (613) in a non-contact force transmission mode, thereby solving the sealing problem; and the elastic modulus of the concrete member (2) is calculated by means of acceleration data obtained by the probe (613), the loss amount of the elastic modulus is then obtained, and real-time in situ monitoring is carried out on freeze-thaw damage of the underwater concrete member (2).

Description

In-situ monitoring device and method for freezing and thawing damage of underwater concrete components

Technical field:

The invention belongs to the technical field of durability monitoring of concrete structures, and relates to an in-situ monitoring device and method for freezing and thawing damage of underwater concrete components. Bit evaluation.

Background technique:

In cold regions or freeze-thaw environments, the moisture in the internal pores of concrete components produces frost heave stress due to freezing, resulting in different degrees of damage to concrete components, which adversely affects safety and durability. In the prior art, the device and method for testing the elastic modulus of concrete members on site are mainly applicable to concrete members on land, for example: a device for measuring elastic modulus of concrete with a level disclosed in Chinese Patent 201710222638.3, including an upper ring and a lower ring, The upper and lower rings are arranged up and down, and both the upper and lower rings are provided with fastening devices for fixing the concrete to be tested; the upper ring is also provided with a circular level, and between the upper and lower rings is fixed a The positioning plate is used to fix the distance between the upper ring and the lower ring; a dial indicator bracket is arranged on the upper ring, and a contact rod is arranged on the lower ring, and the distance between the dial indicator bracket and the contact bar is used for A dial indicator is placed; it calculates the value of the elastic modulus of the concrete through the micro-deformation between the fixing frames. A portable dynamic elastic modulus measuring instrument controlled by a mobile terminal disclosed in Chinese Patent No. 201810780463.2 includes: a host, a transmitter and a receiver. The host includes a broadcast module, a device connection module, a processor and a lithium-ion battery. The host It is a cuboid. The broadcast module, device connection module, processor, and lithium-ion battery are installed inside the host. The transmitter and receiver are outside the host. The transmitter and receiver are connected to the host through cables, and the mobile terminal is connected to the device of the device. The modules are connected one-to-one and have two-way wireless communication through the broadcast module. The device connection module is used to send the device identification information to the target mobile terminal before the broadcast module broadcasts, so that the mobile terminal can accurately and quickly control the device. The broadcast module is used to transmit the information between the mobile terminal and the device. The processor is used to control the switch and adjustment of the transmitter and the receiver, and at the same time convert the information received by the broadcasting module into digital signals, and transmit the signals to the transmitter, the receiver transmits the detected signals to the processor, and the processor transmits the signals to the processor. Convert and send to the mobile terminal via the broadcast module. The mobile terminal is used to control the device, calculate data and display the result, wherein the calculation data and the display result refer to the mobile terminal performing a series of calculations such as Fourier transform on the received data through its own processor to obtain the resonance frequency. , displays the real-time occurrence frequency, the spectrogram at the current frequency and the current amplitude frequency. After the sweep is completed, the resonance frequency is automatically displayed to calculate the dynamic elastic modulus. The mobile terminal can control the device by downloading the social client or offline app; it obtains the resonance frequency by measuring the frequency and amplitude of the test piece through a series of calculations such as Fourier transform, and uses the resonance frequency to calculate the dynamic elastic mode. quantity. A method for measuring elastic modulus of concrete based on surface-pasted PZT disclosed in Chinese Patent No. 201810188114.1 includes the following steps: Step S1: send a preset excitation signal to the PZT exciter attached to the surface of the concrete to be measured; Step S2: Use the PZT sensor array to receive the velocity measurement signal generated by the PZT exciter, and obtain the Rayleigh wave velocity CR according to the received velocity measurement signal, wherein the velocity measurement signal is generated by the PZT exciter being stimulated by the preset excitation signal Step S3: obtain the concrete elastic modulus E through the Rayleigh wave velocity CR; it measures the Rayleigh wave velocity through the PZT exciter and PZT sensor array pasted on the concrete surface, and according to the Rayleigh wave velocity The elastic modulus of concrete is obtained. However, underwater concrete components are exposed to low temperature and high pressure for a long time, and are more prone to freeze-thaw damage than those on land, and the special underwater environment makes the current elastic modulus testing device unable to function. Therefore, at this stage, the test of the mechanical properties of underwater concrete components is mostly realized by the method of coring underwater by divers and carrying out the elastic modulus on land, which will not only bring certain danger to the life of underwater operators, but also obtain The test results of the elastic modulus of the concrete are limited by factors such as season, temperature, time and economic conditions, and are not continuous and representative, and cannot accurately evaluate the degree of freezing and thawing damage of concrete components. Therefore, it is of great significance to test the in-situ elastic modulus of the existing underwater concrete components to evaluate the degree of freeze-thaw damage.

Invention content:

The purpose of the present invention is to overcome the shortcomings of the prior art that the freeze-thaw damage of underwater concrete members cannot be monitored in real time and continuously in situ, and seeks to design an in-situ monitoring device for freeze-thaw damage of underwater concrete members based on elastic modulus and method.

In order to achieve the above purpose, the main structure of the in-situ monitoring device for freezing and thawing damage of underwater concrete components involved in the present invention includes an upper connecting rod, a concrete component, a transverse sealing box, a longitudinal sealing box, a moving guide rod, a probe launching box, a multi-channel Data collector, FM transmitter, computer, auxiliary wheel, lower connecting rod and wireless temperature sensor; one end of the upper connecting rod is connected with the concrete member, the other end is connected with the transverse sealing box, and the transverse sealing box is respectively connected with the longitudinal sealing box and the moving guide. Rod connection, the longitudinal sealing box is connected with the probe launching box through the secondary pulley set in the longitudinal sealing box, the probe launching box is connected with the multi-channel data collector, the multi-channel data collector is connected with the computer through the FM transmitter, and the guide rod is moved. Two rows of auxiliary wheels arranged on the probe launching box are connected to one end of the lower connecting rod, the other end of the lower connecting rod is connected to the concrete member, and a wireless temperature sensor is arranged on the lower connecting rod; Pin launch box and wireless temperature sensor connection.

A No. 1 waterproof power supply and a submersible motor are arranged in the transverse sealing box involved in the present invention. The No. 1 waterproof power supply and the submersible motor are connected by a No. 1 wireless switch.

The transmission chain involved in the present invention is sequentially connected with the main pulley, the reel and the secondary pulley through the guide wheel.

The probe launch box involved in the present invention is provided with a No. 2 waterproof power supply and a spring group. The No. 2 waterproof power supply is connected to the electromagnet through the No. 2 wireless switch, and the spring group is connected to a steel plate frame. The right end of the steel plate frame is provided with a No. 1 magnet, the end of the probe launching box is provided with a conduit with an inner hollow structure, the inner end of the conduit is provided with a No. 2 magnet, the outer end of the conduit is provided with a pulley, and the conduit is provided with a launch guide rod A sealing rubber ring is arranged between the conduit and the launch guide rod, and a probe is set at the end of the launch guide rod.

The upper connecting rod and the concrete member and the lateral sealing box, the lower connecting rod and the concrete member and the moving guide rod, and the probe launching box and the auxiliary wheel are all connected by the locking nut, and the lateral sealing box and the probe launching box are connected with the anti-loosening nut. The loose nuts and between the probe launch box and the secondary pulley are sealed, which has a good waterproof effect; the transverse sealing box, the longitudinal sealing box and the probe launching box are electrical sealing boxes made of stainless steel with a thickness of 5mm; The upper and lower connecting rods are made of seamless steel pipes with an outer diameter of 15mm and an inner diameter of 8mm to ensure that the upper and lower connecting rods are evenly stressed and can reduce their own weight; the multi-channel data collector is electrically connected to the probe; The FM transmitter is a two-way FM transmitter; the No. 1 waterproof power supply and the No. 2 waterproof power supply are lithium batteries; the wireless temperature sensor can monitor the water temperature in real time to reflect whether the concrete components are in a freeze-thaw state; the submersible motor is an oil-filled submersible motor; a Magnets No. 2 and No. 2 are strong N-pole magnets; the probes are acceleration probes.

The calculation formula of the elastic modulus of the concrete member is stored in the computer involved in the present invention:

Among them, _E2 is the elastic modulus of the concrete member, the unit is MPa, m is the mass of the probe, the unit is kg, E1 is the elastic modulus _of the probe, the unit is MPa, and _μ2 is the Poisson's ratio of the concrete member, The dimension is 1, R is the equivalent radius of the probe, the unit is m, _vc is the speed of the probe when it hits the concrete member, the unit is m/s, τ is the impact duration of the probe, the unit is s, μ ₁ is the Poisson's ratio of the probe, and the dimension is 1; the equivalent radius R of the probe, the Poisson's ratio μ ₁ of the probe, the elastic modulus E ₁ of the probe and the mass m of the probe are known.

The technical process of the in-situ monitoring method for freezing and thawing damage of underwater concrete components involved in the present invention includes four steps: emitting probes, collecting data, calculating elastic modulus and evaluating freezing and thawing damage:

1. Transmitting probe: When the wireless temperature sensor detects that the water temperature near the concrete member is higher than 0°C, upload the water temperature to the computer, the computer turns on the No. 2 wireless switch, the electromagnet is energized and generates magnetism, and the iron block is sucked into the electromagnet When the steel plate frame moves to the left, the spring group is compressed, the computer turns off the No. 2 wireless switch, the magnetism of the electromagnet disappears, the iron block is released, and the spring group moves the steel plate frame to the right in the process of returning to its original state, and the No. 1 magnet and No. 2 magnet A repulsive force is generated between them, the repulsive force pushes out the launch guide rod, and the probe hits the concrete member;

2. Collect data: After the probe hits the concrete member, obtain the data of the speed of the probe hitting the concrete member and the collision duration, and send the data to the multi-channel data collector, and the data is sent to the computer through the FM transmitter; the computer turns on No. 1 wireless switch, the submersible motor drives the main pulley to rotate, the reel collects the transmission chain transmitted by the main pulley, and at the same time, the transmission chain drives the probe launching box to move up through the secondary pulley, repeat step 1, so that the probe hits different positions of the concrete member, and the The data acquired by the probe is sent to the computer;

When the reel releases the transmission chain, the secondary pulley drives the probe launching box to move down. During the process of the probe launching box moving up and down, the moving guide rod moves between the two rows of auxiliary wheels to guide the probe launching box to move up and down. maintain stability;

3. Calculate the elastic modulus: The computer calculates the elastic modulus of the concrete member in real time according to the data sent by the FM transmitter and the elastic modulus calculation formula, and draws the concrete member in real time through Matlab (matrix laboratory) and Origin (function drawing software). Elastic modulus change curve, analyze the law of elastic modulus changing with time;

4. Evaluation of freeze-thaw damage: According to the elastic modulus of the concrete member obtained in step 3, the elastic modulus change curve and the law of elastic modulus change with time, the freeze-thaw damage of the concrete member is evaluated. When the elastic modulus loss rate reaches 60 %, it is considered that the concrete member has been damaged by freezing and thawing.

Compared with the prior art, the present invention transmits the measured acceleration data to the multi-channel data collector and then transmits it to the computer in real time through the frequency modulation signal transmitter. The elastic modulus of the concrete member is obtained through the calculation formula, and the change curve of the elastic modulus of the concrete member is drawn in real time. The probe that can move up and down is convenient for monitoring the elastic modulus of different parts of the concrete member, realizing simple, fast, accurate and continuous. It measures the elastic modulus of underwater concrete components; its structure is simple, the operation is convenient, and it can be reused. The high-strength magnet of the same pole is used to provide power for the launch of the probe through non-contact force transmission, which solves the problem of sealing. Based on the acceleration data obtained, the elastic modulus of the concrete member is calculated, and then the loss of elastic modulus is obtained, and the real-time in-situ monitoring of the freeze-thaw damage of the underwater concrete member is carried out, which solves the cost of monitoring the freeze-thaw damage of the underwater concrete member. Large, high risk factor, discontinuous data and other problems, to avoid errors caused by human readings.

Description of drawings:

FIG. 1 is a schematic diagram of the main structure principle of the present invention.

FIG. 2 is a schematic diagram of the partial structure principle of the present invention.

FIG. 3 is a schematic diagram of the internal structure principle of the probe launching box involved in the present invention.

FIG. 4 is a schematic diagram of the data transmission principle of the present invention.

detailed description:

The present invention will be further described below by implementing examples and in conjunction with the accompanying drawings.

Example 1:

The main structure of the in-situ monitoring device for freezing and thawing damage of underwater concrete components involved in this embodiment includes an upper connecting rod 1, a concrete component 2, a transverse sealing box 3, a longitudinal sealing box 4, a moving guide rod 5, a probe launching box 6, Multi-channel data collector 7, FM transmitter 8, computer 9, auxiliary wheel 10, lower link 11, wireless temperature sensor 12, transmission chain 13, lock nut 14, No. 1 waterproof power supply 31, submersible motor 32, No. 1 Wireless switch 33, main pulley 34, reel 35, guide wheel 36, secondary pulley 41, No. 2 waterproof power supply 601, spring group 602, No. 2 wireless switch 603, electromagnet 604, steel frame 605, iron block 606, No. 1 Magnet 607, conduit 608, No. 2 magnet 609, pulley 610, launch guide rod 611, sealing rubber ring 612 and probe 613; one end of the upper link 1 of the hollow tubular structure is connected to the concrete member 2 of the underwater structure, The other end is connected with the horizontal sealing box 3 of the rectangular parallelepiped structure, the horizontal sealing box 3 is respectively connected with the longitudinal sealing box 4 of the rectangular parallelepiped structure and the moving guide rod 5 of the inner hollow structure, the horizontal sealing box 3 is provided with a No. The motor 32, the No. 1 waterproof power supply 31 and the submersible motor 32 are connected through the No. 1 wireless switch 33. The submersible motor 32 is provided with a main pulley 34, a reel 35 and a guide wheel 36 with a circular structure, and a circular structure is provided in the longitudinal sealing box 4. The secondary pulley 41 of the shape structure, the transmission chain 13 is connected with the main pulley 34, the reel 35 and the secondary pulley 41 in turn through the guide wheel 36 to form a closed loop, the longitudinal sealing box 4 is connected with the probe launching box 6 of the cuboid structure, and the probe launching box 6 is provided with a No. 2 waterproof power supply 601 and a spring group 602 composed of four springs. The No. 2 waterproof power supply 601 is connected to an electromagnet 604 through a No. 2 wireless switch 603. The left end of the steel plate frame 605 is provided with an iron block 606, the right end of the steel plate frame 605 is provided with a No. 1 magnet 607, the end of the probe launching box 6 is provided with a conduit 608 with an inner hollow structure, and the inner end of the conduit 608 is provided with a No. 2 magnet 609, the outer end of the duct 608 is provided with a pulley 610, the duct 608 is provided with a launch guide rod 611, a sealing rubber ring 612 is set between the duct 608 and the launch guide rod 611, and the end of the launch guide rod 611 is provided with a probe 613 , the probe launch box 6 is connected with the multi-channel data collector 7, the multi-channel data collector 7 is connected with the computer 9 through the FM transmitter 8, and the moving guide rod 5 passes through the two rows of auxiliary wheels 10 set on the probe launch box 6 It is connected with one end of the lower connecting rod 11, the other end of the lower connecting rod 11 is connected with the concrete member 2, a wireless temperature sensor 12 is arranged on the lower connecting rod 11, and the computer 9 is respectively connected with the transverse sealing box 3, the probe launching box 6 and the wireless temperature sensor 12. The temperature sensor 12 is connected; the upper connecting rod 1 is connected with the concrete member 2 and the transverse sealing box 3, the lower connecting rod 11 is connected with the concrete member 2 and the moving guide rod 5, and the probe launching box 6 and the auxiliary wheel 10 are all connected by the locking nut 14; Multi-channel data collector 7 with The probes 613 are electrically connected.

When the in-situ monitoring device for freezing and thawing damage of underwater concrete components involved in this embodiment is used, after the electromagnet 604 is energized, the iron block 606 is attracted, and the steel plate frame 605 compresses the spring group 602. After the electromagnet 604 is powered off, the magnetic force disappears, and the spring group 602 returns to its original state, and drives the steel plate frame 605 to move to the right quickly, so that the No. 1 magnet 607 and No. 2 magnet 609 repel each other, and the repulsive force sends the probe 613 to the concrete member 2 through the launch guide rod 611, resulting in an impact.

The upper link 1 and the lower link 11 involved in this embodiment are connected to the concrete member 2 without damage, which ensures the integrity of the concrete member 2; the main pulley 34 on the submersible motor 32 is connected with the secondary pulley 41 on the probe launching box 6 , the moving guide rod 5 is in contact with the auxiliary wheel 10 on the probe launching box 6, so that the probe 613 can move up and down smoothly; the probe 613 is connected with the multi-channel data collector 7, and the multi-channel data collector 7 is connected with the FM transmitter 8 is connected, the FM transmitter 8 is connected with the computer 9 , so that the data acquired by the probe 613 can be quickly sent to the computer 9 .

Example 2:

The in-situ monitoring method for freezing and thawing damage of an underwater concrete component involved in this embodiment is used to monitor a certain underwater concrete component 2. When the wireless temperature sensor 12 shows that the underwater temperature is higher than 0°C, the water temperature is uploaded to the computer 9, and the computer 9 Turn on the No. 1 wireless switch 33, the submersible motor 32 drives the main pulley 34 to rotate, the reel 35 collects the transmission chain 13 transmitted by the main pulley 34, and the transmission chain 13 drives the probe launch box 6 to move up through the secondary pulley 41, so that the probe 613 Located on the upper end of the concrete member 2, at the same time, the computer 9 turns on the No. 2 wireless switch 603, the electromagnet 604 is energized and generates magnetism, the iron block 606 is attracted to the electromagnet 604, the steel plate frame 605 moves to the left, the spring group 602 is compressed, and the computer 9. Turn off the No. 2 wireless switch 603, the magnetism of the electromagnet 604 disappears, the iron block 606 is released, and the spring group 602 drives the steel plate frame 605 to move to the right in the process of returning to its original state, and a repulsive force is generated between the No. 1 magnet 607 and the No. 2 magnet 609 , the repulsive force pushes out the launch guide rod 611, and the probe 613 hits the concrete member 2; the above-mentioned monitoring is performed on the concrete member 2 every 20cm, and the multi-channel collector 7 collects the speed and collision of the probe 613 against the concrete member 2. The data of the duration is transmitted to the computer 9 through the frequency modulation transmitter 8, and the computer 9 draws the change curve of the elastic modulus of the concrete member 2 in real time through Matlab (matrix laboratory) and Origin (function drawing software), and analyzes the elastic modulus with time. According to the law of change, whether the concrete member 2 is damaged by freeze-thaw is determined according to the principle of whether the loss rate of elastic modulus reaches 60%.

Claims

An in-situ monitoring device for freezing and thawing damage of underwater concrete components is characterized in that the main structure includes an upper connecting rod, a concrete component, a transverse sealing box, a longitudinal sealing box, a moving guide rod, a probe launching box, a multi-channel data collector, FM transmitter, computer, auxiliary wheel, lower connecting rod and wireless temperature sensor; one end of the upper connecting rod is connected with the concrete member, the other end is connected with the transverse sealing box, and the transverse sealing box is respectively connected with the longitudinal sealing box and the moving guide rod. The sealing box is connected with the probe launching box through the secondary pulley set in the longitudinal sealing box, the probe launching box is connected with the multi-channel data collector, the multi-channel data collector is connected with the computer through the FM transmitter, and the moving guide rod passes through the probe Two rows of auxiliary wheels arranged on the launch box are connected with one end of the lower link, the other end of the lower link is connected with the concrete member, and a wireless temperature sensor is arranged on the lower link; the computer is respectively connected with the transverse sealing box, the probe launch box and the The wireless temperature sensor is connected; the calculation formula of the elastic modulus of the concrete member is stored in the computer:
Among them, E2 is the elastic modulus of the concrete member, the unit is MPa, m is the mass of the probe, the unit is kg, E1 is the elastic modulus of the probe, the unit is MPa, and μ2 is the Poisson's ratio of the concrete member, The dimension is 1, R is the equivalent radius of the probe, the unit is m, vc is the speed of the probe when it hits the concrete member, the unit is m/s, τ is the impact duration of the probe, the unit is s, μ 1 is the Poisson's ratio of the probe, and the dimension is 1; the equivalent radius R of the probe, the Poisson's ratio μ 1 of the probe, the elastic modulus E 1 of the probe and the mass m of the probe are known.
The in-situ monitoring device for freezing and thawing damage of underwater concrete components according to claim 1, characterized in that a No. 1 waterproof power supply and a submersible motor are arranged in the lateral sealing box, and the No. 1 waterproof power supply and the submersible motor are connected by a No. 1 wireless switch, and the diving The motor is provided with a main pulley, a reel and a guide wheel.
The in-situ monitoring device for freezing and thawing damage of underwater concrete components according to claim 2, characterized in that the transmission chain is sequentially connected to the main pulley, the drum and the secondary pulley through the guide wheel.
The in-situ monitoring device for freezing and thawing damage of underwater concrete components according to claim 3, wherein the probe launching box is provided with a No. 2 waterproof power supply and a spring group, and the No. 2 waterproof power supply communicates with an electromagnet through a No. 2 wireless switch. Connection, the spring group is connected with the steel plate frame, the left end of the steel plate frame is provided with an iron block, the right end of the steel plate frame is provided with a No. The outer end of the duct is provided with a pulley, the duct is provided with a launch guide rod, a sealing rubber ring is set between the duct and the launch guide rod, and the end of the launch guide rod is provided with a probe.
The in-situ monitoring device for freezing and thawing damage of underwater concrete members according to claim 4, characterized in that the upper connecting rod and the concrete member and the transverse sealing box, the lower connecting rod and the concrete member and the moving guide rod, and the probe launching box and the auxiliary The wheels are connected by locking nuts, and sealing treatment is performed between the lateral sealing box, the probe launching box and the locking nut, and between the probe launching box and the secondary pulley; the lateral sealing box, the longitudinal sealing box and the probe launching box are The electrical sealing box is made of stainless steel with a thickness of 5mm; the upper connecting rod and the lower connecting rod are made of seamless steel pipes with an outer diameter of 15mm and an inner diameter of 8mm; the multi-channel data collector is electrically connected to the probe; the FM transmitter is bidirectional FM Transmitter; No. 1 waterproof power supply and No. 2 waterproof power supply are lithium batteries; wireless temperature sensor can monitor the water temperature in real time to reflect whether the concrete structure is in a freezing and thawing state; the submersible motor is an oil-filled submersible motor; No. 1 magnet and No. 2 magnet All are N-pole strong magnets; the probe is an acceleration probe.
An in-situ monitoring method for freeze-thaw damage of an underwater concrete component, characterized in that the technological process includes four steps: emitting probes, collecting data, calculating elastic modulus, and evaluating freeze-thaw damage:

1. Transmitting probe: When the wireless water temperature sensor detects that the water temperature near the concrete member is higher than 0°C, upload the water temperature to the computer, the computer turns on the No. 2 wireless switch, the electromagnet is energized and generates magnetism, and the iron block is sucked into the electromagnet When the steel plate frame moves to the left, the spring group is compressed, the computer turns off the No. 2 wireless switch, the magnetism of the electromagnet disappears, the iron block is released, and the spring group moves the steel plate frame to the right in the process of returning to its original state, and the No. 1 magnet and No. 2 magnet A repulsive force is generated between them, the repulsive force pushes out the launch guide rod, and the probe hits the concrete member;

2. Collect data: After the probe hits the concrete member, obtain the data of the speed of the probe hitting the concrete member and the collision duration, and send the data to the multi-channel data collector, and the data is sent to the computer through the FM transmitter; the computer turns on No. 1 wireless switch, the submersible motor drives the main pulley to rotate, the reel collects the transmission chain transmitted by the main pulley, and at the same time, the transmission chain drives the probe launching box to move up through the secondary pulley, repeat step 1, so that the probe hits different positions of the concrete member, and the The data acquired by the probe is sent to the computer;

When the reel releases the transmission chain, the secondary pulley drives the probe launching box to move down. During the process of the probe launching box moving up and down, the moving guide rod moves between the two rows of auxiliary wheels to guide the probe launching box to move up and down. maintain stability;

3. Calculate the elastic modulus: The computer calculates the elastic modulus of the concrete member in real time according to the data sent by the FM transmitter and the elastic modulus calculation formula, and draws the elastic modulus change curve of the concrete member in real time through Matlab and Origin, and analyzes the elastic modulus regularity over time;

4. Evaluation of freeze-thaw damage: According to the elastic modulus of the concrete member obtained in step 3, the elastic modulus change curve and the law of elastic modulus change with time, the freeze-thaw damage of the concrete member is evaluated. When the elastic modulus loss rate reaches 60 %, it is considered that the concrete member has been damaged by freezing and thawing.